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Many of those names are likely trademarked by various companies. I'm quite sure that "king cab" is a Nissan/Datsun name. To avoid trademark problems, all the truck makers had to use different names for the same thing.
When the extended cab trucks first came out in the 70's Ford called theirs the Supercab & Dodge called theirs ClubCab & Nissan called theirs the KingCab.